This invention is related to hybrid inner/outer sectored cells in wireless communication systems, and more particularly to antenna configurations in such systems.
Dual server group configuration cells, hereinafter hybrid inner/outer sectored cells, can be used in a wireless communication system to maximize the capacity of the available of spectrum, and to help to reduce the total number of cells required. FIG. 1 shows hybrid inner/outer sectored cell 10. Hybrid inner/outer sectored cell 10 has an inner server group, hereinafter inner communication coverage area 12, and an outer server group, hereinafter outer communication coverage area 14. The available spectrum is divided into 30 kHz carriers. The carriers assigned to hybrid inner/outer sectored cell 10 are divided into an inner group that are used in inner communication coverage area 12 and an outer group that is used in outer communication coverage area 14. In the configuration shown in FIG. 1, outer communication coverage area 14 is further sectored into three sectors 16, 18, 20 each covered by one of three sector antennas at the base station of hybrid inner/outer sectored cell 10. The inner communication coverage area is not sectored, or as known in the industry it is an omni sector, covered by an omnidirectional antenna. An omni inner communication coverage area is desirable over a three sector inner communication coverage area since more capacity is realized when there is one trunk group of channels, instead of dividing the channels of one trunk group among the three trunk groups of three sectors. The trunk group of channels is a group of channels available for assignment to a user on a particular antenna face.
Normally hybrid inner/outer sectored cell 10 having three sectored outer communication coverage area 14 and omni inner communication coverage area 12 can be implemented by adding a dedicated omnidirectional antenna to inner communication coverage area 12. A problem with such a system is that it requires an additional antenna. The additional antenna adds additional installation, maintenance, and lease costs and additional space to the base station. The additional antenna also often detracts form the aesthetics of the surrounding area.
The hybrid inner/outer sectored cell can also be implemented using the same antennas for the inner and outer communication coverage areas, however this requires that the inner and outer communication coverage areas are either both sectored into the same number of sectors, or that they are both omni cell. Unfortunately, this would not allow for a hybrid inner/outer sectored cell as shown in FIG. 1.
The invention solves the above problems by sharing the existing sector antennas at the base station used for the sectors of the outer communication coverage area to create an omnidirectional inner communication coverage area without increasing the total number of antennas. This allows an increase in capacity of the hybrid inner/outer sectored cell without the additional cost and additional space requirements of adding further antennas.
A base station for the hybrid inner/outer sectored cell has one antenna corresponding to each of the sectors in the outer communication coverage area. The base station also has a combiner and a divider. The combiner is in the receive path of the base station. The signal received on at least two of the antennas is combined in the combiner to obtain the uplink signal. The divider is in the transmit path of the base station. The divider provides signal generated by the radios of the base station to at least two of the antennas.